Vehicle headlight

ABSTRACT

A vehicle headlight has a condensing lens in its front portion. At the rear, the reflector has a sausage-shaped cavity with the lamp positioned therein. A shield is positioned at the lower lefthand side of the headlight to reduce light to the oncoming land of traffic.

United States Patent Krinke Oct. 9, 1973 [5 VEHICLE HEADLIGHT 1,814,3287/1931 Oestnaes 240/4136 [75] Inventor: Hfarlan Krinke, May Twp., Cty.FOREIGN PATENTS QR APPLICATIONS Washmgmn 1,537,728 7/1968 France 2404135 R Assignee: Minnesota Mining and 1,545,880 10/1968 France 240/4135R Manufacturing Company, St. Paul, 1,149,920 4/1969 Great Bmam Minn.

Primary Examiner-Samuel S. Matthews [22] Filed 1972 AssistantExaminer-Michael D, Harris [21] Appl. No.: 247,960 Att0rn eyl(inney,Alexander, Sell, Steldt & Delahunt [52] US. Cl..... 240/7.l, 240/4135 D,24(;/4(1/.35 R, 57 ABSTRACT 4 41.36 [51] Int. Cl. F21m A vehicleheadlight has a condensing lens in its from 58 Field of Search 240/4135D 41.35 R the the reflect has a Sausage- 240/4136 shaped cavity with thelamp positioned therein. A shield is positioned at the lower lefthandside of the [56] References Cited headlight to reduce light to theoncoming land of traf- UNITED STATES PATENTS 1,547,757 7/1925 Johnson240/4135 D 7 Claims, 9 Drawing Figures PATENTED 91975 SHEET 2 BF 2Ewmuwm MM DEGREES & Q

Q \\|/|,|l| II III II 1 L m ili lli iilhl H I T 1 llllllili illlililllBACKGROUND OF THE INVENTION The present invention relates to a novelvehicle headlight which directs an image of the filament down thedriving lane to provide high intensity illumination of the driving laneand which projects an image of a light diffuse programmed cavitysurrounding the lamp over adjacent portions of the roadway. In oneaspect the present invention relates to an improved vehicular headlightfor use during high speed freeway, turnpike and divided highway nightdriving.

The present invention provides a vehicle headlamp which projects lightof varying intensity and which controls the area covered by said lightsuch that the high intense light is directed straight down the path ofthe vehicle and that the light of lower intensity is projectedperipherally in a controlled pattern to avoid glare for oncomingmotorists.

DISCUSSION OF THE PRIOR ART A major safety hazard exists with thepresently commercial vehicle headlamps. This hazard exists for tworeasons. The first reason is that with the increased speed limitspermitted on freeways, turnpikes and other divided interstate highways,the driver is presently overdriving his headlamps. The speedsrecommended on most freeways for night driving are between 65 miles perhour and 75 miles per hour. The distance required to stop at 65 milesper hour is 435 feet; the distance required to stop at 70 miles per houris 535 feet; and the distance required to stop at 75 miles per hour is670 feet. The conventional high beams for vehicle headlamps have beenaccepted as adequate illumination for speeds no greater than 55 milesper hour. At 55 miles per hour the automobile requires a stoppingdistance of 290 feet. The bright spot or maximum initial candle powerfrom conventional high beams is 37,000. This bright spot when projecteda distance of 290 feet has an intensity of approximately 0.5 footcandles. These figures will thus show that it is necessary to increasethe intensity of headlamps. As the intensity of headlamps increaseshowever this will also increase the glare to the oncoming motorist.Blinding of the oncoming motorist is the second reason the conventionalvehicle headlights are a hazard.

Many attempts have been made to improve the headlights and reduce theglare for oncoming motorists, and examples of the prior devices forsolving this problem besides the conventional two-state or binary systemwhich has two discrete states of operation designated as high beam" andlow beam using a pair of filaments, includes U.S. Pat. No. 3,341,700.This U.S. patent discusses prior art using a vane disposed in the lampto completely block out light which may be directed by the lens towardthe oncoming motorists lane and a vane which is only partiallytransmissive such that there is not a sharp frontal shadow edge betweenthe visible light and the dark as one looks at the oncoming vehicle oras one sits in the vehicle equipped with such lights and sees a sharpside edge rather than a gradual shadowing or change from light to dark.Other prior art relating to vehicle headlamps is the application ofRaymond H. Anderson, Ser. No. 68,115, filed Aug. 31, 1970, and assignedto the assignee of this application. In this earlier application thelens of the vehicle headlight is focussed on a roundel which providesdiffuse illumination' to said lens from a source positioned rearwardlyof the roundel. A portion of the roundel is 'masked by a'filter or hasless transmissiveness than the remaining portions of the roundel suchthat the intensity of the light is substantially reduced in one portionof the projected beam;

In these prior art constructions some light is lost because of thediffuser or when the light source is focussed to a focal point of theheadlight lens the light output from the face of the headlamp isgenerally uniform over the face of the lamp and is uniform in theprojected beam. Blocking the projected light from said focal point toshield the other driver and by a moving vane operated by the driver orremotely by a light detector does not solve the intensity problem orgive full protection to oncoming motorists.

Thus it is believed that the prior art fails to meet the total objectiveof increasing safety by providing better illumination farther down theroad for the driver of one automobile and at the same time assuringprotection for the oncoming motorists from glare from the headlamps.

SUMMARY OF THE PRESENT INVENTION The present invention has an advantageover the previously known devices in that no movable parts are requiredto provide protection for the oncoming motorist and yet the headlightprovides sufficient illumination for the driver. It is not necessarythat two filaments be utilized to help reduce the glare to the oncomingmotorists or that a driver make an adjustment in response to a judgmentdecision.

The present invention related to vehicle headlamps provides a highintense driving beam for the driver to see a safe distance up the road,enough peripheral light to clearly illuminate overhead and road sideroad signs, and one which will present a dimmed light to the oncomingmotorist as he approaches the vehicle equipped with these lamps so as topermit the oncoming motorist to know the position 'of the oncomingvehicle but yet not be blinded by the glare of these headlamps.

The vehicle headlightof the present invention comprises a housing with acondensing lens mounted in the forward end of the housing and a sourceof illumination mounted in the rearward end of the housing. The housingmay be conical in shape with the lens positioned in the larger forwardend. The source of illumination comprises a filament disposed centrallyin a first surface circular diffuse reflector. The diffuse reflector hasa programmed cavity surrounding the filament. The cavity opening ispositioned at the focal surface of the lens and the cavity in frontelevation is generally allantoic with the filament disposed centrallyalong a generally vertical center line. An arc of the cavity extendsfrom the upper lefthand quadrant toward the center and up into the upperrighthand quadrant generally symmetrically. The filament is mounted atthe focus of DESCRIPTION OF THE DRAWING The present invention will bemore fully described in the following detailed description which refersto the accompanying drawing wherein:

FIG. 1 is a longitudinal sectional view of a vehicle headlightconstructed according to the present invention;

FIG. 2 is a vertical sectional view taken along line 2-2 of FIG. 1;

FIGS. 3, 4, and 6 are sectional views taken along the respective sectionlines 3-3, 44, 5-5 and 6-6;

FIG. 7 is a graph showing isocandle curves of light illumination from alamp according to the present invention superimposed on a picture of afour lane divided roadway;

FIG. 8 is a schematic plan view of a roadway on a graph showing thepattern of light from vehicles equipped with the headlights of thepresent invention; and

FIG. 9 is a schematic plan view of a roadway on a graph showing thepattern of conventional headlamps having two filaments, one for highbeam" and one for low beam and sold by General Motors Corporation asGuide Power Beam lamps of the 6000 series.

The vehicle headlight as illustrated in FIG. 1 comprises aspherical-shaped cover 10 formed of glass or other transparent material,a condensing lens 11, a housing 12 with the cover and condensing lenssupported at the forward end, and a source 14 of illumination comprisinga lamp 15 having a filament 16 and a programmed diffuse reflector means.Housing 12 is generally conical-shaped with the reflector 17 disposed atthe rear end thereof.

The lamp 15 may be a quartz iodine lamp disposed with the filament 16extending in a vertical plane through the reflector 17. In a preferredembodiment the filament 16 is about 0.26 inch long and has a helicalconfiguration with a diameter of about 0.18 inch. The lamp has a colortemperature of 3,200 K with a maximum candle power of 125,000.

The condensing lens 11 is a Fresnel-type lens and has the focal lengthof about 4.84 inches and the filament 16 of the light source is disposedat the focus of the lens. The lens also has an object distance of about4.84 inches and an image distance of infinity, where magnification at600 feet is determined as follows:

Magnification (600)(l2) tan l/0.09 1400 The image of the filament at 600feet would then be 21 feet wide.

Referring now to FIGS. 2 through 6, the reflector 17 is shown insufficient detail that one may be able to reconstruct the shape of acavity 20 therein which is programmed to distribute light of varyingintensity about the axis of the intense spot or beam of light projectedon axis of the headlight from the filament.

In FIG. 2 the cavity 20 is shown in front elevation and the cavity isgenerally allantoic or sausage-shaped and is a deep cavity having anarcuate configuration and a rather short vertical dimension. The openend of the cavity is disposed at the focal surface of the lens which isa curved plane, for the lens used, having a radius of about 2 inches anda diameter or transverse dimension of about 2.8 inches. The focalsurface, as shown defines two dish-shaped areas 21 and 22 above andbelow the reflective cavity 20. The cavity 20 and areas 21 and 22 arepreferably coated with a diffuse reflecting material,

i.e., magnesium oxide, to afford light diffuse reflecting areas each ofwhich may be image points projected through all areas of the lens 11.The cavity 20 has the lamp 15 disposed therein in a generally verticalposition with the filament 16 in a vertical plane through the lens andcavity as shown in FIGS. 1 and 2.

The reflector 17 is provided with means for controlling light from thecavity 20 in the lower lefthand quadrant of said reflector as shown inFIG. 2. This means for controlling light may be a projecting lip from aconvex side wall 24 in the lower lefthand quadrant of the reflectormember or there may, for convenience in manufacture, be a shield 25disposed over a portion of the area 22 and of the cavity 20 in an areain the lower lefthand quadrant as the reflector 17 is viewed in frontelevation. The face of the shield is painted with a very flat blackpaint affording such low reflectivity that it is not a surface fromwhich any illumination is received. The convex wall 24 projects into thecavity to reduce the amount of light blocked and not redirected by theshield 25 and thus heat buildup is reduced. The shield 25 however blocksthe light in the lower lefthand quadrant or controls the intensity ofthe light in that area to avoid any bright illumination emanating fromthis area of the reflector. The light distribution from the rest of thecavity is precisely controlled by the design of the cavity.

Referring to FIG. 2, the upper arcuate wall of the cavity has a radiusof about 1.2 inches from a point 1.4 inches above the midpoint or apoint on the optic axis of the lens 11. The cavity has a width in thevertical plane through the axis of about 0.9 inch, the wall 24 isdefined by a radius of about one inch from a center p0- sitioned about1.03 or 1.05 inches from each of the two coordinates through thereflector center. The rearward wall of the cavity is radiused in thevertical and horizontal plane and the depth of the cavity from the focalsurface is about one-half (0.5) inch. The walls of the cavity have anincline of 5 to 20 with a line parallel to the optic axis. The cavityproduces a light pattern having light of less than 2,000 candlepowervisible at any time to the oncoming motorist after he has moved 4 to 6to the left of the axes of the headlight of this invention, while at thesame time maintaining the same adequate illumination of the driving laneof the vehicle having the headlight to a distance of more than twicethat of the conventional headlight. The headlight of the presentinvention is much more efficient since the filament is at the lens focusas in a spot light and the light pattern from the lamp and cavity isprojected as illustrated on a vertical chart in FIG. 7 and on ahorizontal chart in FIG. 8.

In FIG. 7 isocandle curves are plotted onto a picture of a roadway toillustrate the varying intensity of the light pattern and the positionof the intense light on a roadway. The light beam is projected straightdown the driving lane 33 toward infinity with the curve 26 indicatingthe area having an intensity of 100,000 candlepower. The curve 26 has asmall size and must be aligned with the vertical and the horizontalplanes through the lamp and directed at a spot straight down the road.Extending about this curve are further curves 27, 28, 29 and 30indicating respectfully areas of 20,000 candlepower; 5,000 candlepower;2,000 candlepower; and 1,000 candlepower. Thus, an oncoming motorist ina lane 34 at 10 to 16 on the lefthand side of the vehicle andapproximately 600 feet away from the light would be exposed to theportion of the lamp having an output of less than 2,000 candlepower andat that distance would see a dim light. At 300 feet away the oncomingvehicle is approximately 18 to the left of the lamp, on a typical fourlane divided freeway with 12 foot lanes, with a 60 foot median 35 andwith 84 feet between centerlines, and would see substantially no light.The headlamp of the present invention as seen in FIG. 8 has a highintensity between and 2 from the axis of the headlamp and beyond 4 leftof the axis the lamp corresponds quite generally to the brightness of alow beam conventional lamp, i.e., 2,000 candlepower. This is allaccomplished without any electrical switching or mechanical movementswithin the headlight which effect a change in the useful light for thedriver to effect a change in the glare protection for the oncomingmotorist.

In FIG. 9, the comparable isocandle curves for a conventional GuidePower Beam lamp No. 6014 (50 watts, 13 volts) is shown with the highbeam (solid lines) and low beam (broken lines) overlayed. The center atthe point of intersection of the horizontal and vertical planes has anintensity at high beam of 38,000 candlepower, lines 37 indicate anintensity of 20,000 candlepower, lines 38 of 10,000 candlepower, lines39 of 5,000 candlepower and lines 40 of 1,000 candlepower. A comparisonof FIGS. 7 and 9 will readily indicate the improved safety performanceof the light of the present invention wherein levels of light equal tobelow that of the low beam is directed toward an oncoming motorist and abright driving light is available to the driver.

I claim:

1. A vehicle headlight comprising a housing, a condensing lens mountedforwardly within said housing and a source of illumination mountedrearwardly within said housing, said source comprising a first surfacediffuse reflector means comprising wall members defining a generallyallantoic cavity which is positioned to open forwardly with its centerpoint disposed below the optic axis of the lens and with an arc thereofextending from the upper lefthand quadrant toward the center and then upinto the upper righthand quadrant area as seen in front elevation, afilament positioned within said cavity below said are and at the focusof said lens, and means for reducing light reflection from said cavityin the lower lefthand quadrant area of said reflector means as seen infront elevation.

2. A vehicle headlight according to claim 1 wherein said opening of saidcavity is disposed along the focal surface of said lens.

3. A vehicle headlight according to claim 1 wherein said reflector meansis generally circular and has a concave forward face, the curvature ofwhich corresponds to the focal surface of the lens with the cavityextending rearwardly of said surface.

4. The vehicle headlight according to claim 3 wherein said means forreducing light reflection includes a shield having a very lowreflectivity positioned over the lower lefthand quadrant area of saidreflector means.

5. A vehicle headlight according to claim 4 wherein said cavity has aconvex wall disposed in the lower lefthand quadrant area to reflectlight beneath said shield.

6. A vehicle headlight according to claim 1 wherein said means forreducing light reflection from said cavity has a rearwardly directedsurface and said rearwardly directed surface provides specularreflection for reducing heat absorption.

7. A vehicle headlight according to claim 3 wherein the rearward facingsurface of said shield is polished to afford specular reflection forreducing heat absorption.

1. A vehicle headlight comprising a housing, a condensing lens mountedforwardly within said housing and a source of illumination mountedrearwardly within said housing, said source comprising a first surfacediffuse reflector means comprising wall members defining a generallyallantoic cavity which is positioned to open forwardly with its centerpoint disposed below the optic axis of the lens and with an arc thereofextending from the upper lefthand quadrant toward the center and then upinto the upper righthand quadrant area as seen in front elevation, afilament positioned within said cavity below said arc and at the focusof said lens, and means for reducing light reflection from said cavityin the lower lefthand quadrant area of said reflector means as seen infront elevation.
 2. A vehicle headlight according to claim 1 whereinsaid opening of said cavity is disposed along the focal surface of saidlens.
 3. A vehicle headlight according to claim 1 wherein said reflectormeans is generally circular and has a concave forward face, thecurvature of which corresponds to the focal surface of the lens with thecavity extending rearwardly of said surface.
 4. The vehicle headlightaccording to claim 3 wherein said means for reducing light reflectionincludes a shield having a very low reflectivity positioned over thelower lefthand quadrant area of said reflector means.
 5. A vehicleheadlight according to claim 4 wherein said cavity has a convex walldisposed in the lower lefthand quadrant area to reflect light beneathsaid shield.
 6. A vehicle headlight according to claim 1 wherein saidmeans for reducing light reflection from said cavity has a rearwardlydirected surface and said rearwardly directed surface provides specularreflection for reducing heat absorption.
 7. A vehicle headlightaccording to claim 3 wherein the rearward facing surface of said shieldis polished to afford specular reflection for reducing heat absorption.